Chemical product and process



United States PatentC 2,831,879 CHEMICAL PRODUCT AND PROCESS No Drawing.Application October 27, 1953 Serial No. 380,703

4 Claims. (Cl. 260-439) This invention relates to the new compoundcyclopentadienyl( cyclopentenylcyclopentadienyl)iron and to a processfor its manufacture.

.Until recently, no compounds were known in which iron is attacheddirectly to a hydrocarbon radical. Dicyclopentadienyliron, the firstsuch compound to be discovered, was described by Kealy and Pauson inNature 168, 1039 (1951), and claimed by Pauson in U. S. patentapplication Serial No. 291,567, filed June 5, 1952, now U. S. Patent2,680,756. Various derivatives of dicyclopentadienyliron such as. thealkyl-substituted products disclosed and claimed in Graham et al. U. S.application Serial No. 352,294, filed April 30, 1953, have since beendescribed but there have not been known heretofore any unsaturatedcycloalkyl derivatives of this compound.

There has now been discovered the compoundcyclopentadienyl(cyclopentenylcyclopentadienyl)iron which is a brightyellow crystalline material, melting when pure at 64-65 C. It isinsoluble in water but is soluble in the common organic solvents such asbenzene, alcohol, ether, gasoline and the like. It dissolves in 96%sulfuric acid to give a red-brown solution which presumably contains anoxidized form of the iron compound.

Cyclopentadienyl(cyclopentenylcyclopentadienyl)iron is believed to havethe following structural formula:

It may also be referred to as monocyclopentenyl dicyclopentadienyliron.

X-ray diffraction studies reported by Dunitz and 01'- gel in Nature 171,121 (1953), indicate that dicyclopentadienyliron has a sandwich typestructure in which the apices of the pentagons do not coincide.According to Wilkinson et al. in J. Am. Chem. Soc. 74, 2125 (1952), allfive positions in each of the cyclopentadienyl rings are equivalent, sothat no isomerism with respect to these rings is possible withmono-substituted derivatives.

Cyclopentadienyl(cyclopentenylcyclopentadienyl)iron is made by heatingdicyclopentadienyliron with hydrofluoric acid, which evidently producesa molecular rearrangement to form the desired derivative. Thehydrofluoric acid should be of at least 45% concentration and may beanhydrous. Temperatures of from 30 to 100 C. may be used, the preferredrange being from 85 to 100 C.

After the heating step to form the cyclopentenyl derivative, thereaction mixture is cooled and the prodp 2,831,879 Patented Apr. 22,1958 uct. isolated by conventional means. In one method of separation,the reaction mixture is poured onto ice in order to dilute the excesshydrofluoric acid, the product is extracted with an organic solvent suchas benzene, and is finally isolated by distillation. The product maythen be recrystallized from ethanol. Alternatively, excess hydrofluoricacid can be stripped from the reaction vessel and the product obtaineddirectly by distillation.

Solutions of hydrofluoric acid containing less than 45% hydrofluoricacid do not give satisfactory yields ofcyclopentadienyl(cyclopentenylcyclopentadieny'l) iron. Yields areimproved as the acid concentration is increased, most satisfactoryresults being obtained with anhydrous hydrogen fluoride. Use of theanhydrous acid is more economical than use of aqueous solutions, so longas the excess is recovered and reused. It is necessary that the qualityof the hydrofluoric acid be high. If appreciable amounts of sulfurdioxide or other sulfurcontaining products are present, lay-products areproduced which are diflicult to separate from the desired organo-ironcompound because of the excessive foaming which they produce duringdistillation. Hydrogen fluoride of satisfactory quality is readilyprepared by treating technical grade hydrofluoric acid with manganesedioxide according to the process of my pending application Serial No.236,684, filed July 13, 1951.

Cyclopentadienyl (cyclopentenylcyclopentadienyl) iron may be preparedusing phosphoric acid in place of hydrofiuoric acid, but the yield andquality of the pronot obtained are poor. When sulfuric acid is used, thedicyclopentadienyliron is converted to an oxidized form and thecyclopentenyl derivative is not formed. With hydrochloric acid, the ironcompound is destroyed at the higher temperatures, while no reaction atall occurs at the lower temperatures.

The reaction is carried out at a temperature of from 30 to C.,preferably from 85 to 100 C. The rate of reaction below 30 C.'isimpractically low. At 100 C., reaction is believed to be complete in anhour or less. Higher temperatures are operable but are unnecessary. Thereaction is ordinarily carried out in a closed pressure vessel.

Cyclopentadienyl(cyclopentenylcyclopentadienyl)iron is useful inimproving the combustion characteristics of fuel oils, as disclosed inPedersen U. S. application Serial No. 370,286, filed July 27, 1953. Itis also a valuable intermediate in the preparation of other organo-ironcompounds. Upon hydrogenation, the double bond in the cyclopentenylradical becomes saturated andcyclopentadienyl(cyclopentylcyclopentadienyl)iron is obtained. Thiscompound is also a usefulfuel additive. The cyclopentenyl derivative maybe copolymerized with other olefins to yield products containing iron. Apale yellow product melting at 80 C. is formed when it is heatedtogether with maleicanhydride.

The product of this invention and methods of preparing and using it areillustrated in the following examples, in which parts are by weight:

EXAMPLE 1 A steel pressure vessel is charged with 300 parts ofdicyclopentadienyliron. The air in the vessel is displaced with nitrogenand 1200 parts of technical anhydrous hydrogen fluoride containing lessthan 0.2% sulfur dioxide are distilled into the reactor while agitatingand cooling.

The temperature is raised to 100 C. over a period of three hours and thecharge is agitated at 100 C. for six hours longer. The reaction mass iscooled to room temperature and discharged onto about 11,000 parts of iceand water. The yellow precipitate which forms is filtered, Washed withwater to remove most of the dilute hydrofluoric acid, and dissolved .inabout 880 .parts of benzene. The benzene solution is dried with calciumchloride, clarified, and distilled.

Most .of the benzene is distilled off by heating the solution until'thetemperature of the charge is 200 C. and finally heating to 190 C. at apressure of mm. The reactionproduct 'distills from 175-185" C. at apressure ot'12 mm. while the temperature of the contents of thedistilling flask is 190-238 C.

One hundred sixty-seven (167) parts of distillate are obtained. Thedistillation residue weighs 82parts and contains 15.4% 'Fe, 75.4% C and7.1% H.

The yellow distillate, which melts at 60-65 C. is crystallized from 1200parts of 95% ethyl alcohol. One hundred thirty (13.0) parts ofcyclopentadienyl(cyclopentenylcyclopentadienyl)iron are obtained. Theproduct consists of bright yellow crystals melting at 64-65 C.

vArza.lysis.--Calcd. for'C gH gFe: C, 71.4; H, 6.34; Fe, 22.2; M. W.,252. Found: C, 71.6; H, 6.36; Fe, 22.1; MYW. 245 (in benzene).

The product dissolves in 96% sulfuric acid with a red-brown color. Thecrystals are stable indefinitely. Benzene and alcohol solutions of themshow no changes after many Weeks storage.

EXAMPLE 2 A steel pressure vessel is charged with parts of manganesedioxide and 800parts of anhydrous hydrogen fluoride of a technical gradecontaining 1-2% sulfur dioxide. The temperature of the charge is raisedto 80-85 C. over a period of two hours, and then kept at till-95 C. fortwo hours. This procedure removes the undesirable sulfur impurities.

After cooling to below C. (the boiling point of hydrogen fluoride) 200parts of dicyclopentadienyliron (M. P. 174 C.) are added. Thetemperature of the chargeis raised to 100 C. in three hours andagitation at 100 C. is continued for six hours. The reaction mass .isthen cooled to 10-20 C. and discharged onto about 8000 parts of ice andwater. The yellow precipitate is filtered, dissolved in benzene, anddistilled as described in Example 1. One hundred twenty (120) parts ofcyclopentadienyl(cyclopentenylcyclopentadienyl)iron are thus obtained,which is identical with the product of the preceding example.

EXAMPLE 3 tilled, cyclopentadienyl(cyclopentenylcyclopentadienyl)- ironis obtained in fair yield.

EXAMPLE 4 Hydrogenation ofcyclopentadienyl(cyclopentenylcyclopentadienyl) iron Cyclopentadienylcyclopentenylcyclopentadienyl)iron is readily hydrogenated tocyclopentadienyl(cyclopentylcyclopentadienyl)iron using platinum oxideasa'catalyst and methanol as the solvent. ThecyclopentadienyKcyClopentylcyclopentadienyl)iron is obtained in betterthan yield. It distills at 160-165 C./l0 mm. .and has a freezing pointof 15-16 C.

AnaZysis.Calcd. for C H Fe: C, 70.9; H, 7.09; Fe, 22.05. Found: C, 71.2;H, 7.07;'Fe, 22.0.

EXAMPLE 5 Reaction with maleic anhydride Five parts ofcyclopentadienyl(cyclopentenylcyclopentadienyl)iron, 4.6 parts of maleicanhydride, and'90parts of thiophenefree benzene as solvent areheate'd to150 C. for six hours. The cooled'reaction massis clarified from a smallaniount'of impurities and 'heated 'onthe steam bath'with dilute ammonia.The ammonia-insoluble part (3.4 parts) is crystallized from methanol andidentified as unreacted starting material.

The ammonia solution is acidified cold withhydrochloric acid and 1.3parts of a grey solid are obtained.

The productis once more dissolved in ammonia and precipitatedwithhydrochloric acid. It is then dissolved in 10 parts of chloroformand precipitated'with 20.0 parts of petroleum ether. A pale yellow solid(0.9'par't)*is obtained which melts with decomposition near C.

/inaZysis.-Calcd. for C H FeO C, 61.9; H, "5:44; Fe, 15.20. Found: C,62.3; H, 5.54; Fe, 14.77. i

What is claimed is:

l. Cyclopentadienyl cyclopentenylcyclopentadienyl)- iron.

7.. A process of preparingcyclopentadienyl(*cyclopentenylcyclopentadienyl)iron which comprisesheating dicyclopentadienyliron with hydrofluoric acid of at least 45%concentration at a temperature of from "30 "to' 100 C.

3. A process according to claim 2 in which 'the"-re'action is carriedout at a temperature between and C.

4. A process of preparing cyclopentadienyl(cyclopemteuylcyclopentadienyl)iron which comprises heatingdicyclopentadienyliron with anhydrous hydrogen fluoride under pressureat a temperature of from 30 to 100 C.

References Cited in the file of this patent UNITED STATES .PATENTSWeinmayr ."July 5,.1 954 OTHER REFERENCES

2. A PROCESS OF PREPARING CYCLOPENTADIENYL(CYCLOPENTENYLCYCLOPENTADIENYL) IRON WHICH COMPRISES HEATINGDICYCLOPENTADIENYLIRON WITH HYDROFLUORIC ACID OF AT LEAST 45%CONCENTRATION AT A TEMPERATURE OF FORM 30 TO 100*C.